Phenanthroline based pincer complexes useful as catalysts for the preparation of methanol from carbondioxide

Abstract

The present invention relates to a novel phenonthroline based pincer complexes and process for preparation thereof. The present invention also provides a one pot process for the conversion of carbon dioxide to methanol in the presence of a molecularly defined pincer-type single-site Ru-catalyst and secondary amine. Further the present invention provides the use of phenonthroline based pincer complexes for the esterification of alcohols and hydrogenation of esters under mild conditions.

The invention claimed is: 
     
       1. A phenanthroline pincer complex, wherein said complex is selected from HCl(CO)Ru(Phen-(tBu)PNN) (3), H(CO)Ru-(Phen-(tBu)PNN (4) and H(CO)Ru(η1BH4)(Phen-(tBu)PNN) (5). 
       
         
           
           
               
               
           
         
       
     
     
       2. The phenanthroline pincer complex as claimed in  claim 1 , wherein said complex is used as a catalyst for hydrogenation of lactones to diols and esters to alcohols. 
     
     
       3. The phenanthroline pincer complex as claimed in  claim 2 , wherein said catalyst is used for dehydrogenation of diols to lactones, alcohol to esters and secondary alcohols to ketones. 
     
     
       4. A process for the preparation of a phenanthroline pincer complex comprising the steps of:
 a) adding solution of Lithium diisopropylamide and tBuOK in suitable solvent to a solution of 2-methyl-1,10-phenanthroline (1) in ether at a temperature in a range of 0° to 5° C. followed by stirring the reaction mixture for a period in a range of 30 to 40 minutes to obtain a solution; 
 
       
         
           
           
               
               
           
         
         b) adding a solution of di-tert-butylchlorophosphine in ether to the solution as obtained in step (a) and stirring for a period of 1 to 2 hours at a temperature in a range of −50° C. to −78° C. followed by stirring at temperature in a range of 25° C. to 30° C. for the period in a range of 12 to 14 hours to obtain Phen-PNN-(tBu) ( 2 ); 
       
       
         
           
           
               
               
           
         
         c) mixing the Phen-PNN(tBu) (2) as obtained in step (b), RuHC1(CO)(PPh 3 ) 3  and tetrahydrofuran heating at a temperature in a range of 60° C. to 70° C. for the period in a range of 5 to 6 hours under argon atmosphere to obtain HC1(CO)Ru(Phen-(tBu)PNN) (3); 
       
       
         
           
           
               
               
           
         
         d) adding Sodium bis(trimethylsilyl)amide to the compound of step (c) in C 6 H 6  to obtain H(CO)Ru-(Phen-(tBu)PNN) (4); 
       
       
         
           
           
               
               
           
         
         e) stirring the reaction mixture comprising HC1(CO)Ru(Phen-(tBu)PNN) (3) and NaBH 4  in toluene and ethanol at a temperature in a range of 50° C. to 70° C. for a period in a range of 10 to 15 minutes followed by stirring at a temperature in a range of 25° C. to 30° C. for a period in a range of 4 to 6 hours to obtain H(CO)Ru(η1BH4)(Phen-(tBu)PNN) (5). 
       
       
         
           
           
               
               
           
         
       
     
     
       5. The process as claimed in  claim 4 , wherein the solvent used in step (a) is selected from hexane, heptane, tetrahydrofuran (THF), diethyl ether, toluene, and etheylbenzene.